Sony SMD-HS73

[torin3]

Re: Sony SMD-HS73

Great observation! Since both diode packs take their output directly from the transformer, I wonder if the transformer is starting to go bad? With power off, try checking D12 for shorts.

The screw to the right leg is .3 ohm. I'm having a hard time getting the probes in, so I'm pulling it out to test it.

[jetadm123]

Re: Sony SMD-HS73

Weird, the original measurement for D12 was 13.81V and now it is 17V DC?

Great observation! Since both diode packs take their output directly from the transformer, I wonder if the transformer is starting to go bad? With power off, try checking D12 for shorts.

[torin3]

Re: Sony SMD-HS73

Weird, the original measurement for D12 was 13.81V and now it is 17V DC?

Yeah. Is it possible that whatever is causing the problem is getting worse?

Or maybe when I had the short that blew the fuse it damaged something else as well?

[retiredcaps]

Re: Sony SMD-HS73

The one closer to the top is the 5V one, and the one closer to the CCFL lamp plugs is the 12V. Same readings as I get at CN1. 4.9V lamp off, 5.1V lamp on. 17V lamp off, 12.25V lamp on.

Weird, the original measurement for D12 was 13.81V and now it is 17V DC?

[torin3]

Re: Sony SMD-HS73

The 5V output is regulated, which is why you see so little movement under load. However, the 12V output is unregulated and generally will be at a higher voltage until a load (ccfl circuit) turns on. Once a load is applied, the voltage will drop. 17V does sound a little high, but not totally unusual. One way of checking is measuring the voltage output directly from the diode packs. These are the two devices mounted on the heatsink on the right side of your board. One device outputs 5V and the other 12V. Measure the middle pin of each device for voltage output. Be careful not to short the legs together!

The one closer to the top is the 5V one, and the one closer to the CCFL lamp plugs is the 12V. Same readings as I get at CN1. 4.9V lamp off, 5.1V lamp on. 17V lamp off, 12.25V lamp on.

[jetadm123]

Re: Sony SMD-HS73

The 5V output is regulated, which is why you see so little movement under load. However, the 12V output is unregulated and generally will be at a higher voltage until a load (ccfl circuit) turns on. Once a load is applied, the voltage will drop. 17V does sound a little high, but not totally unusual. One way of checking is measuring the voltage output directly from the diode packs. These are the two devices mounted on the heatsink on the right side of your board. One device outputs 5V and the other 12V. Measure the middle pin of each device for voltage output. Be careful not to short the legs together!

[torin3]

Re: Sony SMD-HS73

Really nice photo. Let me verify the following:


Whether you have a flickering OR a blank screen, you have a steady 5V and 12V output from the power supply? Correct?

When it is blank, the 5V is around 4.9V, and when the lamp is on, it is around 5.1V.

However, the 12V rail is about 12.25V when the lamp is on. But when the lamp is *OFF*, the voltage is between 16.5V and 17V!!

Very odd, since you seem to have fluctuating voltages reaching the OZ960.

Hint: one method of determining which points are connected on a circuit board is with the power off and system unplugged, set your DMM to resistance or continuity and probe the various points. Zero ohms will indicate a short or continuity between those two points. It's not a super accurate method, since you might pick up readings from nearby resistors, but minus a schematic, it's much better than trying to "eyeball" the circuit.

Thanks for the technique. With the 12V rail is acting weird, any suggestions on what to look for in regards to that? I'm planning to start by checking components I can see that are touching the 12V traces and go from there.

[jetadm123]

Re: Sony SMD-HS73

Really nice photo. Let me verify the following:


Whether you have a flickering OR a blank screen, you have a steady 5V and 12V output from the power supply? Correct?

Very odd, since you seem to have fluctuating voltages reaching the OZ960.

Hint: one method of determining which points are connected on a circuit board is with the power off and system unplugged, set your DMM to resistance or continuity and probe the various points. Zero ohms will indicate a short or continuity between those two points. It's not a super accurate method, since you might pick up readings from nearby resistors, but minus a schematic, it's much better than trying to "eyeball" the circuit.

[torin3]

Re: Sony SMD-HS73

Ok, here is the closeup of of the U1 area.

Also, since I've left it on a while, it is now having the lamps on for a longer time frame. Pin 5 is at about 5.4VDC when the lamps are on.

[torin3]

Re: Sony SMD-HS73

What are 5volts pins doing on CN1, steady or coming and going?
Al.

4.88VDC when the lamps are off.

Up to 5.11VDC when the lamps flash on.

[torin3]

Re: Sony SMD-HS73

Let me explain. What's supplied by the manufacturer of the chip is meant as a guide to help the designer understand how the chip works. It is in NO WAY meant to correspond to the configuration of your board. It's up to the designer to determine how much of the chip manufacturer's design they want to use. It could be some of it, or none of it. Since I don't have a schematic and only photos to work from, I have to use something besides words to get the point across. At this point, it's going to be rough if you can't trace the voltage feeding the OZ960.

I didn't think there was an exact correlation, but I was grasping at straws here. I'll post a real closeup if I can of the area, but I really don't see where it is getting the 5VDC from. Unless there is another layer to the board with hidden traces. But it doesn't look like a multi-layer board as far as I can tell.

Ok, trying to get these readings I managed to bump a heatsink to touch a part of frame that wasn't covered in insulation. So, F1 reads no continuity. 2.5A 250V slow blow ceramic fuse.

Heading over to Radio Shanty to get a replacement.

They didn't have ceramic slow blows in the size and amperage I needed. I got a glass slow-blow with the same amperage and voltage ratings, and a fuse holder to wire it in.

Any issues with this? I'll be ordering a ceramic with pigtail connectors with my next order from digikey, so this will only be used while troubleshooting.

[torin3]

Re: Sony SMD-HS73

What are 5volts pins doing on CN1, steady or coming and going?
Al.

Ok, trying to get these readings I managed to bump a heatsink to touch a part of frame that wasn't covered in insulation. So, F1 reads no continuity. 2.5A 250V slow blow ceramic fuse.

Heading over to Radio Shanty to get a replacement.

[jetadm123]

Re: Sony SMD-HS73

Ok, I'm lost here. Looking at the schematic, I see there should be an R1 at 33 ohms in between pin5 and 5VDC. I found a location marked R1 on the bord, but there is no component there, just 2 solder balls. Just for the heck of it I check the resistance, and between each side, it was 102ohms.

Also, the pins aren't matching up in the schematic to what is on the board. Pin 4 on the schematic goes to C9, but on my board it goes to C10. Pin 5 in the schematic goes to C2, but on my board it goes to C9. C2 is on the other side of the board and it is marked E 222M 3KV. If I understand the datasheet it is 2200pF ceramic cap.

Anyway, I don't seem to be able to trace where the circuit goes, as I don't have a schematic for it, and visually following the traces isn't working. The component numbers aren't matching up for the datasheet schematic you attached. I really don't know what to do.

Help?

Let me explain. What's supplied by the manufacturer of the chip is meant as a guide to help the designer understand how the chip works. It is in NO WAY meant to correspond to the configuration of your board. It's up to the designer to determine how much of the chip manufacturer's design they want to use. It could be some of it, or none of it. Since I don't have a schematic and only photos to work from, I have to use something besides words to get the point across. At this point, it's going to be rough if you can't trace the voltage feeding the OZ960.

[alexanna]

Re: Sony SMD-HS73

What are 5volts pins doing on CN1, steady or coming and going?
Al.

[torin3]

Re: Sony SMD-HS73

Check out Figure 1 on the spec sheet. It's really simplified, but should give you a better idea how this chip works. From Fig 1, the cap connected to pin5 has one end at ground and the other end to 5V. The question is: what other components are between that cap and the 5V that causing the low VDD?

Ok, I'm lost here. Looking at the schematic, I see there should be an R1 at 33 ohms in between pin5 and 5VDC. I found a location marked R1 on the bord, but there is no component there, just 2 solder balls. Just for the heck of it I check the resistance, and between each side, it was 102ohms.

Also, the pins aren't matching up in the schematic to what is on the board. Pin 4 on the schematic goes to C9, but on my board it goes to C10. Pin 5 in the schematic goes to C2, but on my board it goes to C9. C2 is on the other side of the board and it is marked E 222M 3KV. If I understand the datasheet it is 2200pF ceramic cap.

Anyway, I don't seem to be able to trace where the circuit goes, as I don't have a schematic for it, and visually following the traces isn't working. The component numbers aren't matching up for the datasheet schematic you attached. I really don't know what to do.

Help?

[jetadm123]

Re: Sony SMD-HS73

Check out Figure 1 on the spec sheet. It's really simplified, but should give you a better idea how this chip works. From Fig 1, the cap connected to pin5 has one end at ground and the other end to 5V. The question is: what other components are between that cap and the 5V that causing the low VDD?

[torin3]

Re: Sony SMD-HS73

Pin5 (VDD) is the voltage supply pin required by the chip to operate. The specs call for a voltage between 4.7-5.5V and is generally supplied by the 5V output of the power supply. If it's bouncing around, then I suggest you check the components connected to that pin to see if anything is open or shorted.

Also, make sure you're still getting a steady 5V and 12V output from the power supply.

If I'm understanding the path from pin 5, it is going through C9 and then to J7 where it jumps directly to ground. Other than going through C9, it appears to follow the same path to ground as pin 6.

[jetadm123]

Re: Sony SMD-HS73

Pin5 (VDD) is the voltage supply pin required by the chip to operate. The specs call for a voltage between 4.7-5.5V and is generally supplied by the 5V output of the power supply. If it's bouncing around, then I suggest you check the components connected to that pin to see if anything is open or shorted.

Also, make sure you're still getting a steady 5V and 12V output from the power supply.

[torin3]

Re: Sony SMD-HS73

May I suggest that you take some voltage measurements off of the OZ960 (U1). Pins 2 (OVP), 5 (VDD), 10 (CMP). Use Pin 6 for ground.


With power off and monitor unplugged, try checking/measuring the capacitance of the cap off of pin 4 (SST) of the OZ960.

I'll get the voltage readings in just a bit. I had to jury-rig some leads for the capacitance reading. My meter than has capacitance (only up to the 20uf range) has just the 4 holes for sticking in cap leads. I tested the leads I made against a 1uf cap I'd tested the normal way and the readings were the same. So I think I'm ok with this method.

C9 = .82uf
C10 = .17uf
C18 - .84uf

(C locations from the photo, not a data sheet)

Edit: Pin 2 mostly at 0VDC, but bounces up to .74VDC
Pin 5 seems to mostly stay around 1.17VDC, but bounces from nearly 0 to up to around 5-6VDC
Pin 10 seems to stay mostly at .47VDC with drops down to about .05VDC and up to about 1.2VDC

[jetadm123]

Re: Sony SMD-HS73

May I suggest that you take some voltage measurements off of the OZ960 (U1). Pins 2 (OVP), 5 (VDD), 10 (CMP). Use Pin 6 for ground.


With power off and monitor unplugged, try checking/measuring the capacitance of the cap off of pin 4 (SST) of the OZ960.